Oh, that winter-dry skin. (Itch, itch.)

That welt from a mosquito bite. (Scratch, scratch.)

The plague of itching has many sources, and it's the mission of the Temple Itch Center to sort everything out and bring itchers much-longed-for relief. Among many different itches, the center focuses especially on chronic itching - any itch that lasts longer than six weeks.

We spoke recently with its founder and director, Gil Yosipovitch, chair of the dermatology department at Temple University Medical School and widely considered a world itch expert.

Why is it important to study itch?

Because it's very similar to chronic pain. It has a lot of commonalities: It's suffering, it's something that we perceive. But it has its unique flavors. In the last decade, this field has grown exponentially. We know a lot more about the mechanisms of itch.

Acute itch, it causes you to scratch and that's it. But when a patient has chronic itch, it's misery. It has cognitive and emotional aspects. It affects millions of patients around the world. Around 13 percent of the adult population has chronic itch sometime in their life. The older you get, the higher the chances that you'll get itch. In one large study we did, 25 percent of those age 65 and older had chronic itch.

A lot of times, itch is related to dry skin. It also can be related to the decay of some nerve fibers. There are a lot of diseases of the skin that cause itch. Eczema is No. 1, but psoriasis is very problematic and also needs to be addressed.

What does the Temple Itch Center do?

I see chronic itch as a disease. It's not enough to just give someone a cream. A lot of times, doctors give antihistamines; it doesn't, in most cases, work. I felt a need to open an itch center in a big city like Philadelphia. We saw more than 1,000 patients over the last two years with chronic itch. Patients come from all over the U.S. These patients have seen a lot of doctors.

We have innovative approaches to try to reduce the symptoms. We also do a lot of educational programs. We have an eczema school where we teach coping mechanisms. Eczema is the major problem of itch in dermatology. There isn't any other eczema school in the U.S.

The Itch Center is very much involved in understanding mechanisms of itch. We do a lot of human studies and we are a leader in brain imaging of itch. The brain has a lot of mechanisms involved in itch perception and scratching. We have animal models to better understand how itch is transferred along the spinal column. We are trying the most advanced new treatments. We also want to understand the genetics of itch; we have a blood bank, and our patients kindly provide their blood.

What's next on the research horizon?

We are very hopeful that in the next five years there will be drugs on the market for chronic itch. At the moment, our patients are getting treatment that is not itch-specific. Now, it will be more specifically targeted. That makes a big difference. As much as I'm interested in research, first of all I want my patients to feel better. We're getting very close to major changes similar to where the pain field was 30 years ago. This is a most exciting time for itchologs - those who study itch.

Physiologically, why do we itch? Is there any benefit?

Animals, both two legged and four-legged, itch. Or scratch. Dogs scratch like crazy. We think fish can itch and scratch. Itch is a protective phenomenon, most probably, a unique kind of signal to stay away from areas infested by mites or insects or bugs. This is another difference between itch and pain. In pain, no one is going to scratch the area. With itch, you scratch to get rid of the insect.

Finally, the universal questions: Why does it feel so good to scratch an itch? And is it OK to scratch what itches, or not?

The skin is a pleasurable organ. Scratching it induces a sensation of pleasure due to the fact that there are some mechanisms of nerve fibers that transmit pleasure.

One of our recent studies looked at the brains of patients with chronic itch. We induced itch in the patients and imaged their brains while they were scratching, then compared it to the brains of healthy people who were scratching. The reward system in healthy people was activated, but in patients with chronic itch it was a lot more, and there was a very high correlation to pleasure. The more itchy you are, the more pleasure you perceive from scratching it.

Longtime studies of ours found that scratching pleasurability differs among body sites. Patients often scratch the back or the ankle, and I never knew why. It's a matter of sensory pathways. The most pleasurable part of the body to scratch is the ankle. I thought it might be the back. Actually, the back is No. 2.

The problem with scratching: It damages the skin's upper layers. It's a vicious circle. One of the issues is, can you produce a pleasurable reaction without damaging the upper layers of the skin? That's a challenge. We've tried looking into it, but it's not so easy.